Switching devices, such as for smart metering or for control of domestic, residential or vehicle power, often comprise a contactor and an actuator, such as a solenoid coil. The switching devices may be for safely connecting or disconnecting power, such as mains electricity. For example, meters or smart meters may be used to control power supply, such as depending on payment or demand.
The switching devices may be subjected to particular currents, such as high short circuit currents. Typically, the contactor will have a moving blade to effect connection or disconnection. A contact on the moving blade will selectively engage a contact on a fixed bus-bar. Electromagnetic repulsion between the moving blade and the bus-bar, such as due to Lorenz forces, may force the moving blade away from the bus-bar. Under high currents, such as due to short circuits, the contacts may be forced apart, resulting in sparking, local heating, damage to the switch or other potential hazards.
The actuator can be activated, such as by pulsing the solenoid coil, to provide a force sufficient to overcome an attractive force between the contacts, such that the contacts can be intentionally separated when desired to effect disconnection. In some embodiments the actuator provides a component of contact pressure to maintain connection between the contacts in particular circumstances. If the switching device does not provide sufficient contact pressure in particular circumstances, the contacts may separate or provide a poor connection. In some circumstances, a particular contact pressure, particularly a constant contact pressure, may allow the contacts to be effectively welded together by current passing therethrough.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.